Unless otherwise indicated herein, the approaches described in this section are not admitted to be prior art by inclusion in this section.
Different types of analog-to-digital converters (ADCs) can convert an analog signal into a digital signal. For example, a continuous time delta sigma (CTDSM) ADC uses a delta-sigma modulator to convert an analog signal to a digital signal. The CTDSM ADC may use a loop filter to move low frequency noise up to higher frequencies outside the band of interest. The out-of-band noise may then be filtered. This may improve the analog-to-digital conversion.
A quantizer in the delta-sigma modulator may receive the output of the loop filter, and perform the analog-to-digital conversion to output a digital signal. A feedback loop of the CTDSM ADC includes digital-to-analog converters (DACs) that then convert the digital output of the quantizer to corresponding analog values. The analog values are then subtracted from the input signal of the loop filter or internal nodes within the loop filter, and the resulting signal is input back into the loop filter and then the quantizer.
Continuous time delta-sigma ADCs may suffer from excess loop delay (ELD). Excess loop delay may be caused by a finite propagation delay between the time the quantizer samples the analog signal and the time that the feedback DACs present the quantized samples back into the loop filter. The excess loop delay may degrade the stability of the CTDSM ADC and needs to be compensated for. For example, the CTDSM ADC may add an independent signal path, such as an additional excess loop delay compensation feedback path to compensate for the excess loop delay. The additional ELD compensation feedback path requires additional components including additional DACs, summers, and differentiators, which are costly in terms of area, power, and loop complexity. Additionally, as the CTDSM ADC varies in configuration, the additional signal path may not be able to compensate for the delay experienced by some of the configurations.